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Skeletal effects of constant and terminated use of sodium risedronate in ovariectomized rats
Aim:
To study the skeletal effects of constant and terminated use of sodium risedronate (Ris) treatment in the ovariectomized (Ova) rats.
Methods:
Ris 5 micrograms.kg-1, s.c., twice a wk. The proximal tibial metaphysis (PTM) were processed undecalcified for quantitive bone histomorphometry.
Results:
(1) Placebo-treated (normal saline) Ova rats were characterized by decreased trabecular area (TA) on d 60, d 81, and d 150 compared with aging controls, and bone resorption was over formation with high bone turnover. (2) Ova rats were treated with Ris for 60, 81, and 150 d (Ris-on) increased. (TA 217%, 108%, and 101%) respectively, vs Ova rats and depressed bone turnover indices to aging control level, but bone mass did not maintain at high level in 150-d group as in the early stage. (3) Ova rats were pretreated with Ris for 60 d and then terminated (Ris-on/off), followed by sequential sacrifice of rats on 21 and 90 d. Withdrawal on 21 d showed the same results as the match-age Ris-on group. Withdrawal on 90 d still maintained cancellous bone mass at a high level vs 150 d Ris-on groups (+26%) and aging control group (+27%).
Conclusion:
Regimen of Ris 60 d on then 90 d off prevented the development of osteoporosis in Ova rats.